1. Technical Field
The present invention relates to a semiconductor device, and in particular relates to a semiconductor device having a vertical super junction structure with a uniform doping profile and a method for fabricating the same.
2. Description of the Related Art
A conventional VDMOSFET has a p-n junction structure composed of an n-type drift doped region and an overlying p-type doped body region. The p-n junction structure is mainly used to withstand a voltage applied to the conventional VDMOSFET. When improving a withstand voltage of the VDMOSFET, it is required that the dopant concentration be reduced and the thickness of the n-type drift doped region be increased. Improvements in the withstand voltage of the p-n junction structure result in an increased specific on-state resistance (Ron) for the conventional VDMOSFET. The Ron of the conventional VDMOSFET is limited by the dopant concentration of the drift doped region and the thickness of the n-type drift doped region. To resolve this issue, VDMOSFET having a super junction structure has been developed to improve the dopant concentration of the n-type drift doped region, so that the Ron of the VDMOSFET can be improved.
The conventional super junction structure is usually fabricated by multi-epitaxy technology (COOLMOS™). The multi-epitaxy technology requires performing several process cycles of an epitaxy growth process, a p-type dopant implantation process and a thermal diffusion process. Therefore, the multi-epitaxy technology has drawbacks of having plenty of processing steps and a high fabrication cost. In addition, it is hard to reduce the dimensions of the VDMOSFET.
Thus, a semiconductor device and a method for fabricating the same that solve or improve the aforementioned problems are needed.